First, the canard of a grand strategy. True, Obama's staff seems bereft of a latter-day George Kennan, peering through the fog of the postwar (or, in our case, post-Cold War) world and devising sound principles for navigating its thickets. But Kennan was dealing with a world of two main powers; today's world is one of fractured power, much of it still very much in flux. Carving firm guidelines in stone would probably be not only impossible but dangerous.

Yes yes a thousand times yes. In fact it has always been dangerous. The foreign-policy establishment in Washington wants Big Ideas all the time, world-historical grand strategy. We've had them. They've tended to do terrible damage when misapplied and made more universal than they were ever meant to be.

Kennan articulated the "containment" doctrine, a grand strategy aimed at containing the spread of communism. Then a couple years later, Harry Truman and Dean Acheson gave us the Truman Doctrine, when the issue was Stalin's adventurism in Greece and Turkey, and control of the Dardanelles, which held that the US must come to the aid by whatever means of any subjugated people.

But then George Kennan himself says in 1966: hey wait a minute fellas, I only ever meant that to apply to Europe, not Southeast Asia. And the Truman Doctrine worked in Greece and Turkey, but its application to Vietnam was absurd, nay, tragic. Ho Chi Minh's people weren't subjugated by Moscow. They were fighting a war of national liberation against the French. We couldn't see that, because by cracky we had a grand strategy in place.

These questions are always hard. But they are always case-by-case, and should be judged on that basis. Obama is right to resist a grand doctrine. They create horrible situations. If you apply the principles of the Libya incursion to Syria, you are at war with Iran. Do we want that? Each situation is different. Let's learn from history instead of yearning for a great soundbite.